Automatic telephone-exchange.



A. E. KEITH & J. & 0.,1. ERICKSON.

AUTOMATIC TELEPHONE EXCHANGE. APPLICATION FILED NOV- ZB. I904- RENEWED MAH- 26. 1917- 1 286, 180. 7 Patentd Non 26, 1918 2 SHEETS-SHEET l.

s w 515/ T 541 A. E KEITH & J. & CLJ. ERICKSON.

-AUTOMATIC TELEPHONE EXCHANGE. APPLICATION FILED NOV. 28. 1904. RENEWED AR. 26. 1911.

1,286,180. v PaitentedNmnjZC, 1918.

2 SHEET-SHEET 2.

. I WM STATES PATENT OFFICE.

ALEXANDER E. KEITH, OF

. filed Iovember 88, 1994, Serial No. 234,521.

To ail whom it may concern:

Be'it known that we, ALEXANDER E.

KEITH, residing at Hinsdale, county of Dupasmndsmte of Illihois, and JOHN ERICK- soxand CHARLES J. Enrc cson, both residing in' ()hicag'o, county of Cook, and State of Illinois, all citizens of the United States, have-invented a new and useful Improveiicnt in Automatic Telephone-l lxchanges, of

which the following is a specification.

Our invention relates to means for en-- jablinl'g the difierent subscribers of an electrim exchange tocall each other by mech- 'anism, preferably automatic, at the central' exchange, such as is shown in our prior Pat- Jent No. 1,151,541, dated August. 24, 1915, of

which this is a divisional application. The main object of our invention is to proide a mechanism by.means of which circuits may be formed and over which electrical impulses may be sent intermittently and alternately, or simultaneously.

With this and other objects in view our invention consists in the improved construction and novel arrangement of parts of an exchange and the calling apparatus therefor,

as will be hereinafter more fully set forth.

' In the accompanying drawin s in which the same reference numerals in icate corres onding parts in each of the views in which tl iey occur: I

Figure 1 isa View of an exchang embodying our invention,

the calling device being shown in front elevation and the parts of the central exchange necessary to show its operation and also its connection'with the calling device being shown diagramatically.

Fig. 2 is a side elevation of the calling de vice.

Fig. 3 is a transverse vertical sectional view ofthe same.-

In the form of calling device which we have shown forcarrying out our invention, ll'indicates an actuator such as the ordinary finger disk, and 2 indicates a circuit closer which is in the form of a segment having fingersor projections 3 around its periphery,

there being one more projection than there are finger hoids in the actuator. The actuator, circuit closer, a stop. arm 4, and also a circuit changer 5 are rigidly secured to a shaft 6 which is jonrnaled in a suitable frame (but insulated therefrom.

The fingers or projections 3 are-inclined Specification of Letters Patent. brighill application filed Kay 4, 1B03,-Seria1 No. 155,582.

- with the fixed HINSDALE, AND JOHN ERICKSON AND CHARLES J. ERICK- son, on onrcaco, ILLINOIS, ASSIGNORS r0 THE STROWGER uc'awca, A conPonArIoN or ILLINOIS.

AUTOMATIC TELEPHONE Patented Nov. 26, 1918.

(Patent No. 1,151,541.) Divided and. this application Renewed March 26, 1917. Serial No. 157,589.

minal 10 when the segment 2 is being re turned to its normal position, able spring 11, but will move it in the opposite direction or away from the terminal 10, when the segment is being moved out of its normal position by the movement of the actuator in making a call.

The contact 10 is insulated fromthe frame 7 but is electrically connected by wire 12 with one of a group of three terminals, 13, 14 and 15, which are insulatingly secured to the frame. The other ends of these terminals are normally separated but are adapted to be forced into contact by a projection 16 on the telephone receiver book 17 which engages with a projection 18 on one sideof one of the terminals, as 13, downward by as by a suitthe weight of the receiver after the call has been completed. The hook when the hook is forcedspectivcly with terminals 23 and 24 which i are so located as to cuit changer 5. and the other bifurcations are connected respcctivel y with the terminals 13 and 14. A wire 25 is connected at one end end of terminal 9 and at the other end with a terminal 26 which is in constant contact with the circuit changer 5, the terminals 23 and 24 being so arranged as to be in alternate contact with the changer as by making the changer of two diameters and locating the terminals on diametrically opposite sides thereof. A flexible terminal 27 is insulatingly secured to the frame 7 with its free end in position to be moved into or out. of engagement with an armor contact point 52 and having. its opposite end grounded, as by wire 28. i

A shouldered lock-plate or in position to be engaged by the cir-" to make a call.

'hen the hook has raised the plate as far as it can by means of the projection 30, the terminal is still held away from the contact by means of another button b t on the terminal which engages with the projection 34 at the end ot the plate. which was originally in contact with the button 32. But as soon as the actuator has been given a partial rotation to makea call the stop arm engages with the under edge of the plate 29 and forces the plate upward until the nose or projection 2-H passes above. the button 33 and permits the terminal 27 to engage with the contact and close. the circuit to the. ground through the wire 28.

The mechanism at the central exchange for establishing the electrical connections between the interconnecting wires of the different, subscribers may be made of any desired construction. The particular mechanism, used by us for changing the circuit from wire 21 to wire 22, so that, after the switch shaft 31 is moved vertically upward, and afterward revolved to the proper place it can then be released to the normal position. is shown diagrammatically in the lower portion of Fig. 1 where 2 indicates the release magnet. (33 the arn'iature lever thereof, and (H a stiff spring to hold said armature in the norn'ial position. The shaft 31 is provided with means .for contacting the terminals of two banks of points, (36 and 67.

35' is a detent shaft upon which are secured two detents 36 and 37 which engage respectively with the teeth of the vertical ratchet 38 and the rotary ratchet 39 on the switch shaft '51 when the instrument is being operated. A spring'it) holds said detents in yielding engagement with said ratchets.

A pin 4-1 projects trom detent shaft 35 and is disposed in the path 01 movement of a bent lever catch-pawl 42, which latter iS yield-ingly held in position by spring 43.

At 44- is a vertical magnet whose armature is attached to lever 4-5 to which is pivoted a pawl for engaging vertical ratchet 38 in operating shaft 31 step by step vertically.

Lever 45 projects to within a short, distance ot' detent shalt 35. so that, when this lever is operated by the vert cal magnet 44:,

the outer end of the. lever is adapted to.

strike the inwardly projecting end of release pawl 42, and remove the latter from engagement with the detent shat't pin 11. and permit the detents 3t; and 37 to be moved by virtue of spring 40. into engagement. respectively, with vertical ratchet 38 and rotary ratchet 39 at the proper time.

'hen the detent shaft 35 is operated so as to remove detents 3t; and 37 from engag-e ment with ratchets 38 and 3! a rod 47. having one end pivotally attached to detent 37 and the other tipped with insulation. contacts with and moves the switch lever is from connection with wire -19 to connection phone receiver from the hook when the lock plate or arm 2! at the calling device. will be moved upward. when stop-arm -l. and the shaft 3. and the linger-hold disk 1 are tree. to move.

Referring to Fig. 1. the operator now places a tinger in contact with linger-hold No. 3, which is pulled down around in the direction indicated by arrow 1*), until the. finger contacts a stop at. the bottom and is witlnlrawn, when finger-hold disk 1 is released and by virtue of spiral spring 11 carried backward, together with shat't i, and connected segment wheel J to the normal position.

In thus manipulating the finger-hold disk,

.the first movement downwardly causes the stop arm 4 to engage with the locking plate or arm 2!) and complete its upward movement which will permit contact spring or terminal 27 to fall into electrical engagement with arm 52 ot' the insulated part 53 which is in electrical connection with pendantterminal 10.

Also in the first movement downwardly, the insulated circuit changer has been moved from the position shown in full lines to the position shown in the segmental broken lines in Fig. 1, out of contact with switch spring. or terminal 24 and into contact with switch spring or terminal 23.

In the second or backward movement, on

account of segment wheel 2 having one more,

of the four above described, the circuit cha er disk 5 has been moved from the positlon in contact with spring 23 to contact with spring 24, so that this last impulse passes from battery 51 through wire 54, wire 59,-wire 56, auxiliary clectro-magnet 57 and line wire 22, spring 24, disk 5, spring 26, wire 25, spring arm 9, pendant terminal 10, part 53, arm 52, spring 27 and Wire 28. to ground,

causing the auxiliary electro-magnet 57, to

operate the switch arm 48 so that line wire 21 is moved out of connection with wire 50 and into connection with wire 49, which leads to the rotary electro-magnet 58.

Thus far main switch shaft 31 has been lifted three steps, and connection established with the rotary magnet, which before was cut out of circuit.

If now, the finger-hold disk is moved from the fifth hole to the stop, and six impulses sent over the line wires, five, of these impulses would pass from battery 51 through wire 59", electro-magnet 58, wire 49, then the moved switch arm 48, wire 21, spring 23, disk 5, spring 26, wire 25, spring arm 9, pendant arm 10, part 53, arm 52, spring 27 andwire 28 to ground and thereby causing rotary magnet 58 to revolve shaft 31 five steps.

lVhen the disk 5 changes the circuit from line wire 21 to 22 the effect is to simply operate the armature of auxiliary magnet 57, which would have no effect upon switch lever 48 since it would be in the second position in connection with wire 49.

In'the manner described the switch shaft '31 would now have a wiper arin in electrical connection with contact point No. 35 of some subscribers line not shown. y

In the operation of release, a subscriber hangs the telephone on the hook when arm l7 descending in the manner hcreinbcfore described, causes the switch'springs 13 and 14 to first contact, and .thus connect line wires 21 .and' 22, then they are groundedsimultaneously by being brought into contact with spring 15,'which causes a simultaneous current over both main lines 21 and '22, with the result, that the auxiliary magnet is operated to close springs 60 and 61, when current passes from battery 51, through wires 54 and 59, springs 60 and 61, wire 68, release magnet 62, wire 69, to line 21, springs 13, 14 and 15, wire 12, contact point 10, its support 53, contact 52, terminal 27 and wire '28 to groun l.' As the current passes through magnet 62 its armature 63 is attracted which permits the hook arm attached thereto,

. to engage withthe in lave r41,which and withdraws, the. pawls 36, and 37 to the position shown clear of ratchets 38' and 39 and moves the rod 47 so as to return the switch lever when the main switch shaft 31,,

' is" free to returnto its normal or initial'position by virtue of gravity andthe spring at the lower end portion.v 1

' ,We claim as our invention:

1. The combination of two electric circuits extending from a subscribers calling station to the central exchange, a calling device at the subscribers station, said calling device having provisions for changing the circuit with which it is connected at ea'clno eration, switching mechanism at the cen ral exchange adapted to be connected with said circuits, and a single releasing magnet for resioring said switching mechanism to norma.

, 2. The combination of twoielectric circuits extending from a subscribers station to a telephone exchange, a, calling device at the V subscribers station, said device having a circuit closer and a circuit changer, and also having provisions wherebyv the circuit changer connects the circuit closing device with either one or the other. of said circuits, and switching-mechanism at the exchange adapted for connection with said circuits.

3. The combination of two electriccir cuits, a calling device comprising a circuit closer and a circuit changer and having pro visions whereby the circuit changer connects the circuit closer with first oneand then the other of said circuits during operation of the calling device, and switching mechanism at the telephone exchange adapted to be connected with said circuits.

4. The combination with a pair of electric circuits, of a calling device at a subscribers station, said calling device comprising a circuit closer and a circuit changer and having provisions whereby the circuit changer shifts the connection of the callingdevice from one circuit to the other at the close of the operation of the calling device, and switching mechanism at a telephone exchange adapted for connection with saidcircuits.-

5. The combination with two electric circuits, of a'calling device at a subscribers station, said calling device comprising a circuit closer adapted for closing the circuit a,v

euit, and switching meehanisin at a telephone exchange adapted for eonneetion with said circuits.

6. The eombination with two eleetrie-eir euits, of a calling de\'iee having aeireuiteloser adapted to elose the eireuit a plurality of times at eaeh operation and also having a eireuit ehanger adapted to eonn'eet the calling deviee with either one or the other of said eireuits. said ealling deviee having provisions whereby the eireuit ehanger shifts eonneetion from one eireuit to the other during the operation of the eireuit eloser so that all but one of the eurrent impulses eaused by the eireuit eloser pass over one line and the last one passes over the other line. and s\\'itehing meehanism at a telephone exehange eomprising two motor devices ineluded in separate loeal eireuits and an eleetromagnet eombiued with a switch for eonneeting one ol said eleetrie eireuits with one and the other ot' said loeal circuits. said ele-etromagnet being ineluded in said last mentioned line eireuit and the eireuit ehanger ot' the ealling deriee being adapted to eause the eurrent impulses to pass first over the eireuit arranged tor eonueetion with said loeal eireuits and then over the eireuit eontaining said eleetromagnet.

7. A- deviee ot' the eharaeter deseribed comprising .an eleetrie eireuit ineluding a eireuit-eloser at the ealling station. s\\'it('li ing meehanism eomprising a plurality of motor deviees eontrolled by the eiren'it eloser. means tor inserting said motor de' 'viees alternatel in the eireuit. two deriees arranged for alternate operation and eontrolling the said inserting means, and a single releasing magnet t'tn' restoring said deviees to normal.

Shln a telephone system. two, eireuits extending to the substation. switehing meehanism eomp'rising a plurality of motor deviees. a de\'iee tor automatiealtv inserting said motor deviees alternatelv in one eireuit, said inserting deriee having eontrolling means ineluded in the other eireuit. and having an auxiliary eontrolling deviee adaptedfor inelusion in one eireuit. eireuit elosing meeh-anism adapted to he thrown into and out ot"operation. and an additional eireuitelosi'ng means adapted for operation independent;ot' said eireuit elosing me hanism, tor elosing the eireuit in whieh the auxiliary eontrollingderiee is ineluded. substantially as set forth.

S). In a telephone system. a subseriber's line, a ealling deviee therefor. motor deviees For switehing meehauism. a eireuit in whieh these deviees are adapted to be alternately inserted. a eireuit-eloser in the eireuit controlled l said ealling deviee and adapted when operated to eontrol the inserted motor de\'iee. a plurality ot independent means eontrolling the insertion of said motor de- \'i('es in their eireuit. and mechanism arranged to aetuate one of the controlling means.

1t). deviee .ot the eharaeter described eomprising motor deviees for switching meehanism. a eireuit in whieh these deviees a adapted to be alternately inserted. a eireuit-eloser in the eireuit and adapted when operated to eontrol the inserted motor deviee. independent eleetrieall) aetuated means eontrolling the insertion of the motor deviees in their eireuit. a eontaet deriee in eireuit with one ot' said eontrolling means, and loelcing meehanism aetuated in unison with the eoutaet deriee for holding the eirenit-eloser out ot operation. substantiall ias set forth.

ll. deviee ot the eharaetei deseribed eomprising two eleetrie eireuits. a eireuiteloserat theealling station.switehing meehaiiisin eomprising motor dei'iees alteruatel insertible in one and the same eireuit and when so inserted adapted to be eontrolled b said t'll'tlllt-t'ltisel. means ineluded in the other eireuit and eontrolling the insertion of the motor deviees in their eireuit. and a eireuit-ehanger at the sub-station tor automatieallv inserting the motor deviees in the eireuit thereot. substantialtv as set forth.

l2. de\'iee ot the eharaeter deseribed, eomprisingan eleetrieeireuit ineludinga eireuiteloser at the ealling station. switehing meehanism eomprising a 'plu'ralit of motor deriees eont rolled by the eirenit-eloser. means for inserting the motor deriees alternately in the eireuit. deriees t'or reversel operating the inserting means. and meehanism eon trolled b the operation of one and arranged to eontrol the operation of theother ot' the said re\'ersel o ierating de\'iees. substan-.

tially as set t'orti.

l3. de\'iee ol' the ehai'aeter deseribed eomprising an eleetrie. ei-reuit-eloser at the station. sailehing meehanism eomprising :l|)llll1.lllt of motor deviees eontrolled by the ireuit-eloser. means for inserting the motor deviees alternatetv in the eireuit. deriees tor reversely operating the inserting means. means adapted to aetuate I one of said re\ersel operating desires. and meehanism eontrolled by the other of said re\'ersel operating deviees. aml arranged to insert said tirst-named reversely operating deviee in the eireuit. substantially as stated.

11. deviee ot' the ehara ter deseribed eomprislng two eleetrie eii'eilits. a eireuiteloserat lheealling station.s\\'itehingmeehanism at the exehange eoniprising a plurality "of mbtor devices controlled thereby and in mouse sertible in one circuit, and inserting means,

devices for reversely operating said inserting means, one of sald reversely operating devices being included in each circuit, one of said devices consisting of a single magnet for restoring both of said devices to normal.

15. In a telephone system, two electric circuits extending'to the substation, a circuitcloser at the calling station, and switching mechanism comprising a plurality of motor devices controlled thereby and insertible in one circuit, an inserting means, a device for operating the inserting means in one direct1on and included in the other circuit, and a device insertible in the first named circuit for operating the said inserting means in the other direction, substantially as stated.

16. In a telephonesystem, two electric circuits extending to the substation, a circuitcloser at the calling station, and switching mechanism comprising a plurality of motor devices controlled thereby and insertible in one circuit, and inserting means, devices for reversely operating the nserting means, one. of said reversely operating devices being 1nnism at the calling station for controlling the insertion-of said motor devices in circuit with the circuit-closing means, and a .release mechanism for returning the motor devices to their initial positions, substantially as set forth.

18. A device of the character described comprising an electric circuit includinga circuit-closer at the calling station, alternately operating motor devices for switching mechanism insertible, in the circuit, another circuit including means for controlling the insertion of said motor devices in their circuit, means included inthe first named cirouit for removing the inserted motor device therefrom, and contact means for closing said circuits, substantially as set forth.

.19. A device of. the character described .comprising an electric circuit including a circuit-closer at the calling station, alternately operating motor devices insertible in the circuit, another circuit includin means for controlling the insertion of sai motor devices in theircircuit, means for removing the inserted motor device therefrom, coir gm moans for-closing. and. circuits, and

means for holding the. circuit-closer out of operation, when the contact means is actuated, substantially as set forth.

20, In a telephone system, two electric cir cuits extending to the substation, motor de-'-' vices controlled thereby, a switch for the motor devices in one'of said circuits, a magnet in the other, release mechanism adapted to be controlled by said magnet, means for actuating said switch in one direction automatically, and manually operated means for closing the circuit to actuate the release mechanism, substantially as set forth.

21. In a telephone system, two electric circuits extending to the substation, motor'devices controlled thereby, a switch for said motor devices in one of said circuits and release mechanism adapted to be controlled by the other, a magnet for controlling the movement of the switch in each direction, one of said magnets also controlling the release mechanism, substantially as set forth.

22. In a telephone system, two electric circuits extending to the substation, switching mechanism controlled thereby, a switch in one of said circuits and release mechanism adapted to be controlled by the other, a magnet for controlling said release mechanism,

and means for moving said switch in one direction and simultaneously therewith passmg a current through said magnet, substare tially as set forth.

23. In a telephone system, two electrician cuits extending to the substation, switchin mechanism controlled thereby, a side switc mechanism and release mechanism, a magnet for controlling each of said mechanisms, and

means for passing a current through the re-' lease magnet only when the side switch magnet is energized, substantially as set forth.

24. In a telephone system, two electric circuits extending to the substation, switching mechanism controlled thereby, a switch and release mechanism, a magnet'for controlling said switch and release mechanism, an angular lever ada ted to simultaneousl o theswitchan close a circuit through t lease magnet, and another magnet for o rating said lever, substantially as set fort crate e re 25. In a telephone system, two electric cir 5 cuits extending to the substation, switchin' mechanism at the central oflice controlle thereby, a magnet in each circuit, a switch, means controlled by one magnet for moving said switch in one direction, and means 0on1 trolled by the other magnet for movin it in the other direction, said last magnet a one controllin the release of said mechanism, substantia ly as set forth.

26.111 a telephone system two electric cir: cuits extending to the substation, switching mechanism controlled thereby, a ineg'net in each circuit, a switch and release mfihaniem, a leverfor each magnet, oneof "which is adapted to move the switch in one direction and the other one is adapted to control the release, and means connected with the release for n'ioving the switch in the opposite direction, substantially as set forth.

27 A device of the character described comprising two electric circuits, switching mechanism controlled thereby, a magnet in each circuit, a switch lever, released mechanism including a spring-pressed ratchet shaft for engaging with the switching mechanism, a lever connected with the armature of each magnet, one of which moves the switch lever in one direction and the other one controls the shaft, and a rod connected with the shaft for moving the switch lever in the opposite direction, substantially as set forth.

QSJA device of the character described comprising two electric circuits, swi. hing mechanism controlled thereby, a magnet in each circuit, a switch lever, release mechanism including a spring-pressed ratchet shaft for engaging with the switching mechanism,

a pin on said shaft, a lever connected with the armature of each magnet, one of which moves the switch lever in one direction, a catch pawl connected with the other lever for engaging with said pin, means for disengaging said lever from the pin, and a rod connected with the shaft foranoving the switch lever in the opposite direction, sub-' stantially as set forth.

2!). In a telephone system, two electric circuits extending to the substation, each of which is provided with a magnet and one of them w h two terminals, switching mcchanisin controlled by said circuits, a switch leve'r, release mechanism, means connected therewith for moving said lever in one direction, means for moving said lever in the opposite direction, and a single release inag net for controlling the release of said mechanism. substantially as set forth.

30. in a telephone system, two electric circuits extending to the substation. motor devices controlled thereby, a switch controlled over one of said circuits and a magnet in the other, release mechanism adapted to be conti'ollcd by said magnet, and means including said magnet for simultaneously operating said switch and release mechanism. substantially as set forth.

31-. In a telephone system, lines divided into groups, a switch including a contact arm having vertical motion to sclcct groups and rotary motion in a plane at right angles thereto to connect with a line in thc predeteri'nined group, a magnet for causing the.

vertical motion, a magnet. for caiising the ,rotary motion, a circuit controller. 'and incans operated over the line to successively bring said magnets under the control of said circuit controller, including an arm adapted by one movement to open circuit through the first magnet and close circuit through the second magnet.

32. In a telephone system, lines divided into groups, a switch including a contact arm having vertical motion to select groups and rotary motion in a plane at right angles thereto to connect with a line in the predc termined group, a side switch successively controlling the circuits of the operating i'nagnets thereof.

33. In a telephone system, lines divided into groups, a switch including a contact arm having vertical motion to select groups and rotary motion in a plane at right angles.

thereto to connect with a line in the predetermined group, a switch wiper, a plurality of controlling magnets adapted to be successively brought into circuit with said wiper, and means including a magnet for controlling said wiper.

3-4. In a telephone system, lines divided into groups, a switch including a contact.

arm having vertical motion to select groups and rotary motion in a plane at right angles thereto to connect with a line in the predetermined group, a pair of operating magnets,

a relay mechanism, a circuit controller, means operated by said relay mechanism to first o )en circuit throu h one ma net and to thereafter closc circuit through the other, to remove one magnet from thecontrol of said circuit controller. and a line circuit for controlling said rclay mechanism 35. [n a telephone system, lines divided into groups, an automatic switch including a contact arm having one motion to select groups, and then another motion in a ilane at right-angles to the first motion to find a line in the selected group, an electroinaguet controlling the actuation of said switch, a

line over which the said magnet is controlled, another magnet; controlled over the same line for disconnecting the first magnet therefrom, and a single release magnet for controlling the release of said switch.

36. In a telephone system, a circuit, an automatic switch, a controlling therefor included in said circuit, and an electrt'imagnet. autoinatically controlled over magnet switch having a line Wiper, a magnet for moving said wiper in one plane, a second magnet for moving said wiper in a second plane a step-by-step switching device for shifting connection from said first magnet to said second magnet, 21 single release magnet for controlling the release of said stepby-step switching device and said auto matic switch and a switching magnet for controlling said step-by-step switching device, said switching magnet having under its control a one step switch for controlling the circuit of said release magnet.

39. In a telephone system, a suhscrihers station and a line therefor, a calling device at the station adapted at each operation thereof to transmit automatically a series of impiilses over one side of the line fol lowed by a final impulse over the other side of the line, a switching mechanism controllable over the said line and having primary and secondary operating magnets responsive to successive series of impulses, and switchingmeans responsive to said final impulses to shift the control from. one magnet to the other.

40. In a telephone system, a subscribers line, a switching mechanism having primary and secondary operating movements and controllable over said line, a calling device at the station on said line adapted upon suc cessive operations thereof to transmit successive series of impulses over the line to control the movements of said switching mechanism, and a circuit controller in said a switching mechanism responsive to the last impulse of a series to cause the change over from one movement to the other.

41. In a telephone system, a subscribers line, a calling device at the station on said line comprising a pair of cooperating contact members, subscriber controlled means adapted at each operation to cause said contact members to make and break contact with each other a plurality of times to produce current changes in the said line, an automatic switch at the exchange, and a plurality of operating magnets and an electro magnetic circuit changer in said switch all adapted to be controlled by said contact members, the said circuit changer being effective to shift the control of said contact members from one of said magnets to the other.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

ALEXANDER E. KEITH. JOHN ERECKSON. CHARLCS .l. ERICKSON. ll'itncsses ll". 3 Born, ll". Les CA MPH-ILL. 

